...No one expects a midterm turnout to approach that of a presidential year, which generates more excitement and interest. For decades, turnout rates in midterms have been 10 or more percentage points below those of presidential elections. Democrats say their focus group interviews show that two-thirds of those not planning to vote this year don’t even know that an election is being held. And voters historically turn against the party of the president elected two years before.

But there are ways to increase voter participation this year, and some are being tested on a broad scale:

BIG REGISTRATION DRIVES Georgia, where a highly competitive Senate race is taking place, has about 900,000 black, Hispanic and Asian residents who are eligible to vote but are unregistered. Getting even a fifth of them to the polls could make a major difference. (Mr. Obama lost the state by 205,000 votes in 2008.) The New Georgia Project, an effort to register hundreds of thousands of minorities, young people and single women, has already put 85,000 new names on the registration lists. This has infuriated Republicans, including the highly partisan secretary of state, Brian Kemp, who has accused the group of fraud and begun a trumped-up investigation.